First make sure you have PowerShell installed.  In this example I used PowerShell 1.0

After you have successfully installed powershell execute the following in powershell

Set-ExecutionPolicy RemoteSigned

The above command will allow you to install any script that you create.  It will also allow you to install downloaded scripts from the Internet only if they have been signed by a trusted publisher.

Now you will need to download VMWare vSphere PowerCLI, current version is VMWare vSphere PowerCLI 4.0 Update 1. 

Once you have everything installed open up the vSpherePowerCLI.

Issue the “Connect-VIServer” command   –without the quotes

Enter the IP address of the VMWare server, one you are done hit enter twice.  Most likely you will get an SSL certificate error unless you have already trusted the SSL certificate of your VMWare server.  A windows login prompt will come up where you will have to login.

Once you are logged in it will look like the screen below

Now issue the following command

“(Get-VMHost | Get-View).Summary.Hardware.OtherIdentifyingInfo[1].IdentifierValue”  –without the quotes

This will display the service tag of the machine.  Currently this has only been tested on Dell machines, but should work the same for HP.